Air conditioning system with vapor injection compressor

ABSTRACT

An air conditioning system can be toggled between a heating mode, in which heat is withdrawn from a source (e.g., a geothermal source) and deposited into a conditioned space (e.g., a building), and a cooling mode, in which heat is withdrawn from the conditioned space and deposited into the source. The air conditioning system uses a combination of efficiency-enhancing technologies, including injection of superheated vapor into the system&#39;s compressor from an economizer circuit, adjustable compressor speed, the use of one or coaxial heat exchangers and the use of electronic expansion valves that are continuously adjustable from a fully closed to various open positions. A controller may be used to control the system for optimal performance in both the heating and cooling modes, such as by disabling the economizer circuit and vapor injection when the system is in the cooling mode.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/150,821, filed on Oct. 3, 2018, which is continuation of U.S.application Ser. No. 14/862,762, now U.S. Pat. No. 10,119,738, which wasfiled on Sep. 23, 2015, which claims the benefit of and priority to U.S.Provisional Patent Application No. 62/056,082 filed on Sep. 26, 2014entitled AIR CONDITIONING SYSTEM WITH VAPOR INJECTION COMPRESSOR. Theseapplications are incorporated by reference herein in their entirety.

BACKGROUND 1. Technical Field

The present disclosure relates to air conditioning systems and, inparticular, to efficient-enhanced reversible air conditioning systemscapable of both heating and refrigeration.

2. Description of The Related Art

Heating and cooling systems may include a compressor for compressing aworking refrigerant fluid, a condenser heat exchanger for extractingheat from the refrigerant fluid, an expansion valve, and an evaporatorheat exchanger for extracting heat from an external source. In someinstances, such refrigeration systems may further include an economizerheat exchanger and/or a vapor injection feature associated with thecompressor for increasing both the capacity and the efficiency of thecompressor.

In typical refrigeration systems, the refrigerant is a high pressure hotliquid upon leaving the compressor, is a high pressure warm liquiddownstream of the condenser, is a low pressure warm gas downstream ofthe expansion valve, and is a low pressure cool gas downstream of theevaporator.

An economizer may be used to further influence the thermal state of therefrigerant between the condenser and evaporator. An auxiliaryrefrigerant flow is tapped from the main refrigerant flow downstream ofthe economizer heat exchanger and passed through an expansion valve toexpand the auxiliary refrigerant flow before same is passed back throughthe economizer heat exchanger in heat exchange relation with the mainrefrigerant flow. This serves to further subcool the main refrigerantflow upstream of the evaporator.

The economizer heat exchanger also discharges an auxiliary refrigerantflow in the form of an intermediate pressure vapor, which is theninjected into the compressor. Typically a scroll compressor is used inconnection with such a system, and the vapor is injected at anintermediate pressure location within the wraps of the scrollcompressor.

Further increases in efficiency and capacity are desirable in airconditioning systems, in order to increase system efficacy and/ordecrease the cost of operating the system.

SUMMARY

The present disclosure provides an air conditioning system which can betoggled between a heating mode, in which heat is withdrawn from a source(e.g., a geothermal source) and deposited into a conditioned space(e.g., a building), and a cooling mode, in which heat is withdrawn fromthe conditioned space and deposited into the source. The airconditioning system uses a combination of efficiency-enhancingtechnologies, including injection of superheated vapor into the system'scompressor from an economizer circuit, adjustable compressor speed, theuse of one or more coaxial heat exchangers and the use of electronicexpansion valves that are continuously adjustable from a fully closed tovarious open positions. A controller may be used to control the systemfor optimal performance in both the heating and cooling modes, such asby disabling the economizer circuit and vapor injection when the systemis in the cooling mode.

BRIEF DESCRIPTION OF THE DRAWINGS

The above mentioned and other features and objects of this invention,and the manner of attaining them, will become more apparent and theinvention itself will be better understood by reference to the followingdescription of embodiments of the invention taken in conjunction withthe accompanying drawings, wherein:

FIG. 1 is a schematic illustration of an air conditioning system inaccordance with the present disclosure, illustrating refrigerant flow ina heating mode;

FIG. 2 is another schematic illustration of the air conditioning systemshown in FIG. 1, with refrigerant flow reversed for a cooling mode;

FIG. 3 is an elevation view of a scroll compressor including vaporinjection in accordance with the present disclosure;

FIG. 4 is a perspective view of a coaxial heat exchanger used in the airconditioning system shown in FIG. 1;

FIG. 5 is an elevation, cross-sectional view of a portion of the coaxialheat exchanger shown in FIG. 4, illustrating fluid flow therethrough;

FIG. 6 is an elevation, cross-section view of a flash tank used in someair conditioning systems for separating entrained liquid from vapor; and

FIG. 7 is a schematic view of a geothermal air conditioning system inaccordance with the present disclosure.

Corresponding reference characters indicate corresponding partsthroughout the several views. Although the exemplifications set outherein illustrate embodiments of the invention, the embodimentsdisclosed below are not intended to be exhaustive or to be construed aslimiting the scope of the invention to the precise form disclosed.

DETAILED DESCRIPTION

For purposes of the present disclosure, “air conditioning” refers toboth heating and cooling a conditioned space (e.g., the inside of abuilding). In particular and as described in detail below, an airconditioning system may be reversible to cool a conditioned space whileexhausting heat to a source (e.g., a geothermal source), or to heat aconditioned space by extracting heat from the source.

For purposes of the present disclosure, “superheated vapor” refers to avapor whose temperature is measurably above its liquid/vapor phasechange temperature for a given vapor pressure.

For purposes of the present disclosure, “subcooled liquid” refers to aliquid whose temperature is measurably below its liquid/vapor phasechange temperature for a given ambient vapor pressure.

For purposes of the present disclosure, “vapor mixture” refers to mixedliquid-and-vapor phase fluid in which the fluid can undergo phasechanges (i.e., from liquid to saturated vapor or from saturated vapor toliquid) at constant pressure and temperature.

Referring generally to FIGS. 1 and 2, the present disclosure providesair conditioning system 10 which is reconfigurable between a heatingmode (FIG. 1) and a cooling mode (FIG. 2). Such reconfiguration may beaccomplished by actuation of a four way reversing valve 14, whichreverses the direction of refrigerant flow among the various componentsof system 10, thereby reversing the flow of heat to and from a source S(e.g., a geothermal source) and a load B (e.g., the interior of abuilding or other thermally conditioned space). System 10 may furtherinclude an economizer heat exchanger 20 which enables a vapor injectionfeature to enhance the efficiency and function of the compressor 12 inthe heating mode, but may not be needed in the cooling mode. Asdescribed in detail below, the toggling of reversing valve 14 from theheating mode to the cooling mode may be accompanied by adjusting aneconomizer expansion valve 24 to cease refrigerant flow therethrough,effectively disabling the vapor injection in the cooling mode.

Regardless of whether air conditioning system 10 is utilized for heatingor cooling a conditioned space, the same set of components all remaindisposed in the system flow path, the specific functions of which arediscussed in detail below. System 10 includes compressor 12 fluidlyconnected to load heat exchanger 16 and source heat exchanger 18 viareversing valve 14. Operably interposed between load heat exchanger 16and source heat exchanger 18 is economizer heat exchanger 20. Primaryexpansion valve 22 is operably interposed between economizer 20 andsource heat exchanger 18, while economizer expansion valve 24selectively receives a portion of the refrigerant flow and discharges toeconomizer 20 in the heating mode. In the cooling mode of FIG. 2,economizer expansion valve 24 prevents one of the two flows ofrefrigerant through economizer heat exchanger 20, effectively nullifyingthe effect of economizer 20 on the thermal characteristics of airconditioning system 10, as also described in detail below.

1. Reversible Heating and Cooling

Air conditioning system 10 is configured as a reversible heat pump. In aheating mode, refrigerant flow through system 10 sends hot refrigerantthrough load heat exchanger 16, which operates as a condenser depositingheat Q₁ into a conditioned space B, while cold refrigerant is sentthrough a source heat exchanger 18 which operates as an evaporator towithdraws heat Q₃ from a source S, e.g., a geothermal source. In acooling mode, the roles of load and source heat exchangers 16, 18 arereversed, as described further below such that load heat exchanger 16operates as an evaporator and source heat exchanger 18 operates as acondenser.

FIG. 1 illustrates air conditioning system 10 in the heating mode.Compressor 12 receives refrigerant in a low-pressure superheated vaporphase at compressor inlet 30 and vapor injection inlet 32, as describedbelow, and compresses this refrigerant vapor into a high pressure,superheated vapor phase thereby increasing the temperature, enthalpy andpressure of the refrigerant. This hot vapor phase refrigerant dischargesat compressor outlet 28 into fluid line 34, which conveys the vapor toreversing valve 14. Valve 14 passes this superheated vapor to fluid line36, which conveys the vapor to the compressor-side port 38 of load heatexchanger 16.

Load heat exchanger 16 is in thermal communication with a conditionedspace B, which may be a residence or other building, for example, andoperates to exchange heat Q₁ between the refrigerant and a working fluidand thereby send heat Q₁ to conditioned space B. In particular, thesuperheated refrigerant vapor received at port 38 discharges heat Q₁ toa relatively cooler working fluid circulating through working fluidlines 42 between building B and load heat exchanger 16. The heatedworking fluid exits at crossflow outlet 38A of load heat exchanger 16,carrying heat Q₁ which is subsequently deposited in building B. Forexample, building B may have a radiant heat system which extracts heatQ₁ from the working fluid and then sends cooled fluid back to crossflowinlet 40A of load heat exchanger 16, where the working fluid is againallowed to circulate through heat exchanger 16 to absorb heat Q₁ fromthe hot refrigerant vapor. Other heating systems for building B may beused in accordance with the present disclosure, such as forced-airheating systems or any other suitable heat transfer arrangement.Moreover, the refrigerant may transfer heat to a circulating workingfluid which deposits heat in building B, or warmed working fluid mayitself be deposited into building B directly, such as hot water beingdirected into a hot water heater for consumption in building B, directrefrigerant-to-air heat transfer (e.g., by blowing air over hot heatexchanger coils into building B), and the like.

The removal of heat Q₁ from the refrigerant as it passes through loadheat exchanger 16 effects a phase change from superheated vapor (at thecompressor-side port 38) to a partially subcooled liquid (ateconomizer-side port 40), which is discharged to fluid line 44 andconveyed to the load-side port 46 of economizer heat exchanger 20. Therefrigerant flows through heat exchanger 20, which removes heat Q₂therefrom as described below. Upon discharge from economizer heatexchanger 20 at the source-side port 48, the full volume of refrigerantflow passes through fluid line 50A to fluid divider 51, where a mainflow of refrigerant continues toward source heat exchanger 18 via fluidline 50B, while a portion of the refrigerant is diverted into fluid line52A and flows toward economizer expansion valve 24.

At expansion valve 24, subcooled liquid refrigerant is allowed to expandinto a low-pressure, cool liquid- and vapor mixed-phase state. Pressuresensing line 54A is fluidly connected to expansion valve 24, such thatthe pressure within valve 24 can be monitored remotely, e.g., bycontroller 70 (further described below). The low-pressure, mixed-phaserefrigerant discharged from valve 24 is transmitted through fluid line52B to a crossflow inlet 48A of economizer 20 where it circulates inheat-transfer relationship with the main refrigerant flow until reachingcrossflow outlet 46A. During this circulation, heat Q₂ transfers fromthe warmer main flow of liquid refrigerant passing from port 46 to port48 to the low-pressure flow of the economizer portion of refrigerant,such that the refrigerant is warmed to a low-pressure superheated vaporby the time it discharges at outlet 46A. This superheated vapor iscarried by vapor injection fluid line 54B to vapor injection inlet 32 ofcompressor 12.

The transfer of heat Q₂ also serves to further lower the temperature ofthe subcooled liquid phase refrigerant exiting the source-side port 48,as compared to the liquid phase refrigerant entering at the load-sideport 46. As noted above, a main flow of this lower-temperature subcooledliquid phase refrigerant passes divider 51 and flows through fluid line50B to primary expansion valve 22. In valve 22, the sub-cooled liquid isallowed to expand into a low-pressure, cold, mixed liquid/vapor phase.This cold fluid is conveyed via fluid line 56A to a filter/dryer 26,which separates entrained liquid from the vapor and discharges the coldliquid and vapor to fluid line 56B, which conveys the refrigerant to theeconomizer-side port 60 of source heat exchanger 18.

The cold mixed-phase refrigerant received at economizer-side port 60passes through source heat exchanger 18, receiving heat Q₃ from workingfluid circulating through source heat exchanger 18 from source S,thereby warming up to a low-pressure, superheated vapor phaserefrigerant which is discharged at the valve-side port 62. Source S maybe, for example, a geothermal source which is at a consistently warmertemperature than the cold refrigerant received at the economizer-sideport 60. Cooled working fluid is circulated from crossflow outlet 60A,through working fluid lines 64 circulating through source S where theworking fluid is warmed, and back to source heat exchanger 18 atcrossflow inlet 62A. The warmed working fluid is then ready to dischargeheat Q₃ to the cold refrigerant as noted above.

In an exemplary embodiment, the working fluid circulating through loadheat exchanger 16 may be, e.g., water, while the working fluidcirculating through source heat exchanger 18 may be, e.g., water,methanol, propylene glycol, or ethylene glycol.

The low-pressure, superheated vapor discharged from the valve-side port62 of source heat exchanger 18 is conveyed via fluid line 66 toreversing valve 14, where it is allowed to pass to fluid line 68, whichin turn conveys the vapor to compressor inlet 30 to be compressed forthe next refrigerant cycle.

Turning now to FIG. 2, a cooling mode of air conditioning system 10 isillustrated in which refrigerant flow is substantially reversed from theheating mode of FIG. 1, and the discharge of heated vapor fromeconomizer 20 to compressor 12 is ceased such that vapor injectionfunctionality is operably disabled.

To reverse the refrigerant flow direction from heating to cooling mode,4-way reversing valve 14 is toggled to the configuration of FIG. 2.Thus, as illustrated, hot superheated vapor phase refrigerant dischargedfrom compressor outlet 28 is conveyed to the valve-side port 62 ofsource heat exchanger 18 via fluid line 34, valve 14, and fluid line 66.Rather than transferring heat to the conditioned space of building B viaload heat exchanger 16 as shown in FIG. 1 and described in detail above,source heat exchanger 18 now serves as a condenser to extract heat fromthe hot vapor phase refrigerant, and deposit the extracted heat Q₃ atsource S by thermal exchange between the refrigerant and the workingfluid circulating through fluid lines 64.

Subcooled liquid exits source heat exchanger 18 at the economizer-sideport 60 and passes through filter 26 as described above. The subcooledliquid then passes through primary thermal expansion valve 22, where therefrigerant is expanded to a cold vapor/liquid mixture and discharged tofluid line 50B. At fluid divider 51, no refrigerant flow passes to fluidline 52A toward economizer expansion valve 24, but rather, the entirevolume of refrigerant passes from line 50B to line 50A and on toeconomizer 20. Thus, no fluid circulates from crossflow inlet 48A tocrossflow outlet 46A of economizer 20, and therefore no substantial heattransfer occurs within economizer heat exchanger 20. Thus, the coldvapor/fluid mixture which enters economizer 20 at the source-side port48 exits the load-side port 46 with substantially unchanged temperature,pressure and phase.

In order to stop the diversion of refrigerant flow at divider 51 andtherefore effectively disable economizer 20, economizer expansion valve24 may be adjusted to a fully closed position. This prevents fluid flowtherethrough, such that no fluid passage through fluid lines 52A, 52Band 54B occurs. In an exemplary embodiment, valve 24 is an electronicexpansion valve (EEV) which can be continuously adjusted between fullyclosed and fully opened positions, as well as any selected intermediateposition. Advantageously, the use of an EEV for economizer expansionvalve 24 allows controller 70 to control valve 24 automaticallyaccording to a programmed set of instructions. As described in detailbelow, controller 70 may automatically adjust valve 24 to a fullyclosed, zero-flow position when air conditioning system 10 is toggledfrom the heating mode to the cooling mode. However, it is contemplatedthat economizer expansion valve 24 may be a thermostatic expansion valve(TXV) together with a solenoid operable to separately permit or preventflow therethrough. The thermostatic expansion valve may change the sizeof its fluid flow passageway responsive to pressure and/or temperaturechanges, while the solenoid operates as an open/closed only valve.

Referring still to FIG. 2, the lack of fluid flow through economizerexpansion valve 24 also results in a lack of flow through vaporinjection fluid line 54B, such that no vapor is injected at vaporinjection inlet 32 of compressor 12. Accordingly, the vapor injectionfunctionality provided in the heating mode of FIG. 1 is operablydisabled and the cooling mode of FIG. 2 by the closure of expansionvalve 24.

The mixed vapor/liquid phase refrigerant discharged at the load-sideport 46 of economizer 20 is carried to economizer-side port 40 of loadheat exchanger 16 by fluid line 44, where heat Q₁ is transferred to thecool vapor mixture from building B. In particular, cooled working fluidcirculates from crossflow outlet 38A, through working fluid lines 42 andinto building B, where the working fluid is warmed by the ambient air ofbuilding B. This warmed working fluid is carried by working fluid lines42 back to crossflow inlet 40A of load heat exchanger 16, where the flowof the relatively colder vapor/liquid refrigerant absorbs heat Q₁, suchthat the refrigerant is converted to a superheated vapor phase by thetime it is discharged at the compressor-side port 38. Fluid line 36conveys the superheated vapor through valve 14 to fluid line 68, andthen to compressor inlet 30, where the low-pressure superheated vapor isagain compressed for a new refrigerant cycle.

Advantageously, the disabling of the vapor injection functionality inthe cooling mode, while enabling the same in the heating mode, allowsefficiency gains to be realized in a reversible heat pump system. Inparticular, compressor 12 operates with relatively high compressionratios in the heating mode of FIG. 1, in order to provide the requisiteheat for conditioning building B by deposit of heat Q₁ therein. Thus, inview of the larger work load borne by compressor 12 during the heatingmode, a vapor compression functionality as shown in FIG. 1 and describedin detail above provides substantial increases in capacity andefficiency of air conditioning system 10. However, in the cooling modeof FIG. 2, compressor 12 may utilize lower compression ratios betweeninlet 30 and outlet 28 while still providing adequate removal of heat Q₁from building B. At these lower compression ratios, vapor injection isunnecessary and that functionality may therefore be disabled without anefficiency penalty. Advantageously, the operable disabling of vaporinjection may be accomplished entirely by controller 70 e.g., by issuinga command for economizer expansion valve 24 to fully close whenreversing valve 14 to toggle from the heating to the cooling mode.

2. Variable-Speed Scroll Compressor

In an exemplary embodiment, compressor 12 is a variable speedscroll-type compressor. Scroll compressors, also known as spiralcompressors, use two interleaving scrolls to pump fluid from an inlet toan outlet, such as by fixing one scroll while the other orbitseccentrically without rotating, thereby trapping and pumping orcompressing pockets of fluid between the scrolls. Advantageously, thesuperheated vapor received at the vapor injection port may be injectedto the scroll set at an intermediate point of the compression process.The size and position of these ports can be optimized to ensure maximumbenefit and coefficient of performance and capacity for scrollcompressor 12 at expected operating conditions for a particularapplication.

In one exemplary embodiment shown in FIG. 3, compressor 12 includesvapor injection inlet 32 on an outer surface of compressor shell 126,leading to a vapor transfer tube 120 extending into the interior ofcompressor 12 around scroll 122 to manifold 138. Manifold 138 deliversthe vapor to vapor injection outlets 124 via lateral passageway 140formed in stationary scroll 136. Outlets 124 may be positioned alongpassageway 140 at any selected location to correspond with a selectedwrap of scroll 122. Outlets 124 deliver vapor V within working pocketsdefined between the scroll wraps which are at an intermediate pressurebetween the low pressure at inlet 32 (FIG. 1) and the high pressure atoutlet 28 (FIG. 1). Thus, superheated vapor flowing from economizer 20is received at vapor injection inlet 32, and is then delivered via tube120 and outlets 124 to a desired location among the wraps of scroll 122.Advantageously, the particular location of outlets 124 among the wrapsof scroll 122 can be selected for a particular application, in order toprovide superheated vapor to scroll 122 at a desired location formaximum efficiency of compressor 12.

Variable speeds used in compressor 12 further allows precise matching ofcompressor output to the load demanded for a particular application. Inthe embodiment of FIG. 3, scroll 136 is a fixed scroll while moveablescroll 122 may orbited relative to scroll 136 at a variable speed toprovide the variable speed function of compressor 12. In the illustratedreversible embodiment of FIGS. 1 and 2, the variable loads imposed byheating and cooling cycles (as noted above) may be met by varying thespeed of compressor 12. Further, the variable-speed operationfacilitates a steady ramp up and ramp down as compressor 12 changesspeed, such that a refrigerant buffer tank may be kept to a minimalsize.

3. Coaxial Heat Exchangers

In an exemplary embodiment, economizer 20 is a coaxial heat exchanger80, shown in FIG. 4. Coaxial heat exchanger 80 includes outer fluidpassageway 82 with a coaxial inner fluid passageway 84 receivedtherewithin, as shown in FIG. 5. The coaxial arrangement of passageways82 and 84 may form a plurality of coils 86 (FIG. 4) to provide a desiredaxial extent of passageways 82, 84 while consuming a minimal amount ofphysical space. Outer passageway 82 includes axial ends 88 whichsealingly engage the outer surface of the adjacent inner passageway 84,and include inlet 90 and outlet 92 radially spaced from the outersurface of the main axially extending body of outer passageway 82.

An incoming flow F₁ is received at inlet 90, as best seen in FIG. 5, andproceeds to flow around the outer surface of inner fluid passageway 84until reaching outlet 92 where it is discharged as outlet flow F₂.Similarly, an inlet flow F₃ flows into inner fluid passageway 84 atinlet 96, and flows along the opposite axial direction through innerpassageway 84 to be discharged at outlet 94 as flow F₄, while remainingfluidly isolated from the flow through outer passageway 82. This“counter-flow” arrangement, in which the inlet 90 of outer fluidpassageway 82 is adjacent the outlet 94 of the inner fluid passageway 84and vice-versa, promotes maximum heat transfer between the respectiveworking fluids by maximizing the temperature differential throughout theaxial extent of coaxial heat exchanger 80. However, in some instances,one of the fluid flows may be reversed so that both working fluidstravel along the same direction.

In the exemplary embodiment of FIG. 5, inner fluid passageway 84 mayinclude a plurality of corrugations 98 arranged in a helicalthreadform-type pattern, which encourages the development of a twisting,turbulent flow through both outer and inner fluid passageways 82, 84.This flow ensures that the working fluids in passageways 82, 84 remainwell mixed to promote thorough heat transfer between the two fluidsthroughout the axial extent of heat exchanger 80.

Advantageously, employing coaxial heat exchanger 80 for economizer 20 inair conditioning system 10 helps to ensure delivery of sub-cooled liquidto expansion valve 22, while also ensuring that the vapor injection flowthrough fluid line 54B to vapor injection port 32 (FIG. 1) is alwayssuperheated. In particular, the coaxial heat exchanger arrangement shownin FIGS. 4 and 5 provides a large amount of heat transfer between thefluid flows, thereby promoting the provision of pure superheated vaporto the vapor injection port 32 of compressor 12, which may be designedto handle only vapor such as in the case of scroll compressor 12described above. The heat transfer enabled by economizer 20 also ensuresthat only subcooled liquid is provided to expansion valve 22, which mayoperate properly and efficiently (e.g., without “hunting” or erraticadjustment behavior) when pure liquid is delivered.

In a further exemplary embodiment, heat exchanger 80 may be designed tooperate using potable water in one or both of passageways 82, 84. Forexample, coaxial heat exchanger 80 may also be used for load heatexchanger 16, in which the working fluid circulating through workingfluid lines 42 to building B may be water designed to be delivered tothe end user, such as hot water for a hot water heater which dischargesto building appliances. It is also contemplated that source heatexchanger 18 may be a coaxial heat exchanger 80, designed for eitherpotable or non-potable fluid flows.

In some instances, economizer 20 may be formed as flash tank 100, shownin FIG. 6. In this arrangement, a flow F₅ of refrigerant is received atinlet 102 in a mixed phase, such as a partially subcooled refrigerant ofthe type carried by fluid line 44 shown in FIG. 1. This refrigerant isallowed to expand or “flash” into vapor upon entry into flash tank 100.Saturated vapor 104 rises toward outlet 106, passing through ade-entrainment mesh pad 108 to remove any entrained liquid in vapor 104.This drier, but still saturated vapor 110 flows from outlet 106 to thevapor injection port of a compressor, such as inlet 32 of compressor 12via fluid line 54B as shown in FIG. 1. Meanwhile, residual liquid 112collects at the bottom of flash tank 100, the level of which is measuredby fluid level measuring device 114. Depending on the measured level ofliquid 112, a control valve 116 connected at liquid outlet 118 may beopened (to lower the level) or closed (to allow further liquidaccumulation). The sub-cooled liquid 112 may be discharged to anexpansion valve, such as expansion valve 22 via fluid lines 50A, 50B.

However, the provision of saturated vapor 110 to a vapor injection portof a compressor is not optimal, because in some cases such vapor mayinclude droplets of liquid refrigerant, for which the compressor, suchas scroll compressor 12, is not designed. Further, the level of liquid112 within flash tank 100 must be controlled within a given range, andis influenced by the particular refrigerant properties received at flowF₅, as well as the volume of flow. Thus, flash tank 100 must be sizedaccording to other system parameters of air conditioning system 10 inorder to work properly, and the working parameters of system 10 may onlybe changed within a certain range without overwhelming the capacities offlash tank 100. In order to provide flexibility for reversiblefunctionality the exemplary embodiment of air conditioning system 10shown in FIGS. 1 and 2 utilizes coaxial heat exchanger 80 for economizer20, rather than flash tank 100.

4. Transcritical Refrigerant

In an exemplary embodiment, the refrigerant flow used for the thermalcycle of air conditioning system 10 is R410A refrigerant. In airconditioning system 10, R410A may be used in a transcritical cycle,i.e., the refrigerant may be present in both sub-critical andsuper-critical states at different points along its fluid path.

For purposes of the present disclosure, a super-critical fluid is afluid having a temperature and pressure above its critical point, atwhich distinct liquid and gas phases do not exist. For example, the“vapor/liquid mixture” referred to above with respect to the heating andcooling cycles shown in FIGS. 1 and 2 may be super-critical fluids.Sub-critical fluids, on the other hand, are fluids in which distinctliquid and gas phases do exist, such as subcooled liquid and superheatedvapor as described in detail above with respect to the heating andcooling cycles of FIGS. 1 and 2 respectively.

Advantageously, R410A refrigerant can traverse sub-critical andsuper-critical states without itself changing phase, such that a highertemperature refrigerant may be utilized for more effective heat transferat various stages of air conditioning system 10. Moreover, R410A is alsowidely used in homes and buildings for primary heating/cooling needs inthe United States as well as elsewhere in the world, and is readilycommercially available in sufficient quantity for small- or large-scaleheating/cooling needs for a reasonable price. R410A is also generallyaccepted under local, state, and federal codes.

In some applications in accordance with the present disclosure, otherrefrigerant candidates may include R134a, R32, R1234ze, or blends of anyof the previously mentioned refrigerants.

5. Control and Operation

In operation, controller 70 is electrically connected to compressor 12,4-way reversing valve 14, economizer expansion valve 24 and primaryexpansion valve 22, as shown in FIGS. 1 and 2. In the heating mode (FIG.1), controller 70 toggles 4-way reversing valve 14 into the illustratedconfiguration, opens economizer expansion valve 24 to an appropriatefluid flow capacity, and adjusts primary expansion valve 22 to produce adesired vapor mixture carried by fluid lines 56A, 56B from the expectedsub-cooled liquid arriving from fluid line 50B.

Controller 70 activates compressor 12, which sets the heating cycle inmotion by compelling refrigerant to pass through the various functionalstructures of air conditioning system 10 to effect heating in buildingB, as described in detail above. In an exemplary embodiment, controller70 receives signals indicative of fluid pressures within expansionvalves 22, 24, as measured by pressure sensing lines 58, 54A,respectively. Controller 70 includes a comparator which compares thepressures within pressure sensing lines 58, 54A of valves 22, 24,respectively, against a desired pressure for a particular application.This comparison results in a disparity between the desired and actualpressure, which is then compared against a threshold acceptabledisparity. When the actual disparity is beyond the threshold disparity,controller 70 adjusts the fluid flow through valves 22, 24 and/or thespeed of compressor 12 in order to bring the pressure within pressuresensing lines 58, 54A to a level within the desired disparity.

When it is desired to switch from the heating mode of FIG. 1 to thecooling mode of FIG. 2, controller 70 toggles 4-way reversing valve 14from the configuration of FIG. 1 to the configuration of FIG. 2. Inaddition, controller 70 adjusts economizer expansion valve 24 to a fullyclosed position, thereby operably disabling the vapor injection featureused in the heating mode, as described in detail above. Primaryexpansion valve 22 may also be adjusted to the differing demands ofreceiving sub-cooled liquid from fluid line 56A and discharging a vapormixture to fluid lines 50B, as described above.

Controller 70 may then activate compressor 12 in order to compel therefrigerant throughout the refrigerant circuit shown in FIG. 2 andeffect cooling of building B as described above. As with the heatingmode described above, controller 70 may adjust the speed of compressor12 and/or the flow characteristics through valve 22 in order to maintainthe pressure within pressure sensing line 58 in an acceptable range.Generally speaking, the desired pressure within valve 22 and line 58 islower in the cooling mode of air conditioning system 10 as compared tothe heating mode thereof. Therefore, compressor 12 is generallycontrolled by controller 70 to operate at a slower and/or lower powerstate in the cooling mode as compared to the heating mode.

6. Applications.

The present system may be used in the following particularizedapplications.

In an exemplary embodiment, air conditioning system 10 may be used in ageothermal system, in which source heat exchanger 18 is in heat exchangerelationship with a ground source/loop 64 as a heat source/heat sink S.

Air conditioning system 10 may also be used for hot water heating forhydronic applications, such as residential or business heating systemswhich use water as a heat-transfer medium for heating the air inside abuilding. Such systems include radiant-heat applications, for example.In the exemplary embodiment of FIGS. 1 and 2, working fluid lines 42 maycarry hot water to building B, deposit heat Q₁ therein, and recirculateto load heat exchanger 16 to be reheated.

For example, an exemplary geothermal application of air conditioningsystem 10 utilized with forced-air type air conditioning is illustratedin FIG. 7. Air conditioning system 10 is contained within a singlehousing 128, as shown, which also includes air movers (not shown) forinducing air flow F through ducts 42 (in the forced-air context of FIG.7, ducts are the working fluid conduits 42 of FIG. 1 and air is theworking fluid). Source S is a ground source, such as an undergroundformation of soil, rock, water, and the like. In the cooling mode, heatQ₃ is deposited into the underground formation by warm working fluidcirculating through fluid lines 64, and withdrawn from building B asheat Q₁ via ducts 42. Conversely, in the heating mode, heat Q₃ iswithdrawn from the underground formation by cool working fluidcirculating through fluid lines 64, and deposited into building B asheat Q₁ via ducts 42.

As noted above and illustrated in FIG. 7, air conditioning system 10 mayalso be used for domestic or commercial hot water heating. Such systemsconvey hot working fluid from air conditioning system 10 (e.g., fromload heat exchanger 16) through hot water line 132 to a water heater 130which may be located, e.g., in building B. Cool water is returned to airconditioning system 10 (e.g., back to load heat exchanger 16) via a coolwater line 134 to be reheated.

While this disclosure has been described as having exemplary designs,the present disclosure can be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the disclosure using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this disclosure pertains and which fallwithin the limits of the appended claims.

What is claimed is:
 1. A heat pump system for heating and cooling aspace, comprising: a refrigerant circuit through which refrigerant isconfigured to flow; a variable speed compressor disposed on therefrigerant circuit, the compressor including a compressor inlet, acompressor outlet, and a vapor injection inlet disposed between thecompressor inlet and the compressor outlet; a load heat exchangerdisposed on the refrigerant circuit to exchange heat between therefrigerant and either a cooling load or a heating load; a source heatexchanger disposed on the refrigerant circuit to exchange heat betweenthe refrigerant and a source; a reversing valve disposed on therefrigerant circuit between the compressor and the load and source heatexchangers and selectable to effect a heating mode and a cooling mode,wherein in the heating mode the reversing valve routes the refrigerantfrom the compressor outlet to the load heat exchanger and routes therefrigerant from the source heat exchanger to the compressor inlet,wherein in the cooling mode the reversing valve routes the refrigerantfrom the compressor outlet to the source heat exchanger and routes therefrigerant from the load heat exchanger to the compressor inlet; adiverter disposed on the refrigerant circuit between the load heatexchanger and the source heat exchanger, the diverter configured todivert a portion of the refrigerant to an economizer circuit when theheat pump system is in the heating mode and none of the refrigerant whenthe heat pump system is in the cooling mode, wherein the economizercircuit includes: an economizer heat exchanger configured to exchangeheat between the refrigerant diverted to the economizer circuit and therefrigerant in the refrigerant circuit to create superheated refrigerantvapor for injection into the vapor injection inlet, and an electroniceconomizer expansion valve (EEEV) disposed between the diverter and theeconomizer heat exchanger, the EEEV configured to selectively meter andexpand the diverted refrigerant when the heat pump system is in theheating mode and the economizer circuit is active and to selectivelycease diversion of the refrigerant to the economizer circuit when theheat pump system is in the cooling mode; an electronic primary expansionvalve (EPEV) disposed on the refrigerant circuit between the diverterand the source heat exchanger to selectively meter the refrigerantdischarged from the economizer heat exchanger to the source heatexchanger when the heat pump system is in the heating mode and theeconomizer circuit is active and to selectively meter the refrigerantdischarged from the source heat exchanger to the economizer heatexchanger when the heat pump system is in the cooling mode and theeconomizer circuit is inactive; and a controller operable to control thereversing valve, the EEEV, and the EPEV, wherein in the heating mode,the EPEV receives the refrigerant from the economizer heat exchanger anddischarges the refrigerant to the source heat exchanger, wherein in thecooling mode, the EPEV receives the refrigerant from the source heatexchanger and discharges the refrigerant to the economizer heatexchanger.
 2. The heat pump system of claim 1, wherein the controller isconfigured to control the EEEV to meter the diverted refrigerant to theeconomizer heat exchanger.
 3. The heat pump system of claim 1, whereinthe controller is operable to toggle the reversing valve to effect theheating mode and adjustably open the EEEV when the heat pump system iscalled upon to deposit heat into a conditioned space; and toggle thereversing valve to effect the cooling mode and close the EEEV to a fullyclosed position when the heat pump system is called upon to withdrawheat from the conditioned space.
 4. The heat pump system of claim 1,wherein the economizer heat exchanger comprises: a first flow paththrough which the refrigerant in the refrigerant circuit passes; and asecond flow path through which the refrigerant diverted to theeconomizer circuit passes, the second flow path coaxial with, butfluidly isolated from, the first flow path such that the first flow pathis in heat exchange relationship with the second flow path.
 5. The heatpump system of claim 1, wherein the variable speed compressor is avariable speed scroll compressor.
 6. The heat pump system of claim 1,wherein at least one of the load heat exchanger and the source heatexchanger comprises: a first flow path through which the refrigerantpasses; and a second flow path through which a first or second workingfluid passes, respectively, the second flow path coaxial with, butfluidly isolated from, the first flow path such that the first flow pathis in heat exchange relationship with the second flow path.
 7. The heatpump system of claim 1, further comprising a refrigerant filter/dryerdisposed on the refrigerant circuit between the source heat exchangerand the EPEV.
 8. The heat pump system of claim 1, wherein the controlleris operable to compare a detected refrigerant pressure at the EPEV to adesired refrigerant pressure and compute a pressure difference, and ifthe pressure difference is beyond a threshold amount, adjust at leastone of a speed of the compressor and a flow rate of the refrigerantthrough the EPEV to return the pressure difference to an amount lessthan the threshold amount.
 9. The heat pump system of claim 1, whereinthe controller controls the compressor to operate at a slower speed inthe cooling mode than in the heating mode.
 10. The heat pump system ofclaim 1, wherein the load heat exchanger heats or cools potable water.11. The heat pump system of claim 1, wherein the controller is operableto compare a detected refrigerant pressure at the EEEV to a desiredrefrigerant pressure and compute a pressure difference, and if thepressure difference is beyond a threshold amount, adjust at least one ofa speed of the compressor and a flow rate of the diverted refrigerantthrough the EEEV to return the pressure difference to an amount lessthan the threshold amount.
 12. The heat pump system of claim 1, whereinthe refrigerant is R410A and the heat pump system operates therefrigerant in sub-critical and super-critical states.
 13. The heat pumpsystem of claim 1, wherein the source is a geothermal source, and aworking fluid circulates between the source heat exchanger and thegeothermal source to exchange heat between the refrigerant and thegeothermal source.
 14. A method of controlling a heat pump system,comprising: toggling a reversing valve to effect one of a heating modeand a cooling mode, the reversing valve being disposed on a refrigerantcircuit between a variable speed compressor disposed on the refrigerantcircuit, a load heat exchanger disposed on the refrigerant circuit toexchange heat between a refrigerant and either a heating load or acooling load, and a source heat exchanger disposed on the refrigerantcircuit to exchange heat between the refrigerant and a source;determining a first refrigerant pressure in a first pressure sensingline fluidly connecting an electronic economizer expansion valve (EEEV)to a vapor injection inlet of the compressor; controlling the EEEV basedon the first refrigerant pressure, the EEEV being configured toselectively divert a portion of the refrigerant from the refrigerantcircuit to an economizer heat exchanger, the EEEV being disposed on aneconomizer circuit between a diverter and the economizer heat exchanger,the diverter being disposed on the refrigerant circuit, the economizerheat exchanger being configured to exchange heat between the refrigerantdiverted to the economizer circuit and the refrigerant in therefrigerant circuit to create superheated refrigerant vapor forinjection into the vapor injection inlet of the compressor, including:in the heating mode, adjusting the EEEV to meter and expand the divertedrefrigerant, and in the cooling mode, fully closing the EEEV to ceasediversion of the refrigerant; and determining a second refrigerantpressure in a second pressure sensing line fluidly connecting anelectronic primary expansion valve (EPEV) to a compressor inlet;controlling the EPEV based on the second refrigerant pressure, the EPEVbeing configured to selectively meter and expand the refrigerant, theEPEV being disposed on the refrigerant circuit between the diverter andthe source heat exchanger, including: in the heating mode, metering therefrigerant discharged from an active economizer heat exchanger to thesource heat exchanger, and in the cooling mode, metering the refrigerantdischarged from the source heat exchanger to an inactive economizer heatexchanger; and controlling a speed of the compressor based on the firstand second refrigerant pressures to circulate the refrigerant throughthe load heat exchanger, the economizer heat exchanger, the source heatexchanger, and the EPEV to match compressor output to the heating loadand the cooling load.
 15. The method of claim 14, wherein toggling thereversing valve, controlling the EEEV, controlling the EPEV, andcontrolling the speed of the compressor are performed by an electroniccontroller.
 16. The method of claim 15, wherein in the heating mode thecontroller compares the first refrigerant pressure with a desired firstrefrigerant pressure at the EEEV to generate a first pressuredifferential; compares the first pressure differential with a firstpredetermined threshold pressure differential; and adjusts at least oneof the speed of the compressor and a flow rate of the divertedrefrigerant when the first pressure differential is outside the firstpredetermined threshold pressure differential.
 17. The method of claim15, wherein in the heating mode and in the cooling mode the controllercompares the second refrigerant pressure with a desired secondrefrigerant pressure at the EPEV to generate a second pressuredifferential; compares the second pressure differential with a secondpredetermined threshold pressure differential; and adjusts at least oneof the speed of the compressor and a flow rate of the refrigerantthrough the EPEV when the second pressure differential is outside thesecond predetermined threshold pressure differential.
 18. The method ofclaim 15, wherein in the heating mode the controller controls at leastone of the speed of the compressor, a flow rate of the refrigerantthrough the EPEV, and a flow rate of the diverted refrigerant throughthe EEEV to maintain the refrigerant in a mixed liquid-and-vapor phasestate between the EEEV and the economizer heat exchanger and between theEPEV and the source heat exchanger.
 19. The method of claim 15, whereinin the cooling mode the controller controls at least one of the speed ofthe compressor and a flow rate of the refrigerant through the EPEV tomaintain the refrigerant in a mixed liquid-and-vapor phase state betweenthe EPEV and the load heat exchanger.
 20. The method of claim 15,wherein in the heating mode the controller controls at least one of thespeed of the compressor, a flow rate of the refrigerant through theEPEV, and a flow rate of the refrigerant through the EEEV to maintainthe refrigerant in a superheated vapor phase between the load heatexchanger and the compressor, and to maintain the refrigerant in asubcooled liquid phase between the economizer heat exchanger and theEPEV.
 21. The system of claim 1, wherein the EEEV is configured to becontinuously adjustable between fully open and fully closed positions,wherein when the heat pump system is in the heating mode and theeconomizer circuit is inactive the EEEV is closed.